A direct drawing type lithographic printing plate precursor comprising a support having provided thereon an image-receiving layer is now widely used as an office printing plate precursor. For making such a printing plate precursor, that is, for forming images, a method of handwriting images on an image-receiving layer using oil ink, a method of printing with a typewriter, by the ink jet system or the transfer type heat-sensitive system is, in general, adopted. In addition, a method of transferring and fixing the toner image, formed on a photoreceptor through processes of charge, exposure and development using a plain paper copier (PPC), on an image-receiving layer of the printing plate precursor has begun to be used in recent years. In either case, the printing plate precursor after image forming is surface-treated with a desensitizing solution (a so-called etching solution) and a non-image area is desensitized and the resulting printing plate is used as a lithographic printing plate.
In conventional direct drawing type lithographic printing plate precursors, zinc oxide is used as the inorganic pigment in an image-receiving layer. In a direct drawing type lithographic printing plate precursor of a system in which the non-image area after image formation is desensitization-treated and used as a printing plate, in particular, when the printing plate is used in an electrostatic image transfer system, sufficiently transferring a toner image to a printing plate precursor and inhibiting printing smearing as well have been examined using, as zinc oxide, the zinc oxide produced by a wet system, further, using the zinc oxide produced by a wet system in combination with the zinc oxide produced by a dry system (JP-A-5-246166 and JP-A-5-254267 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")), or using zinc oxide containing a small amount of a ferrocyanate group (JP-A-6-72058).
However, there has been a problem in the thus-produced conventional printing plates such that if the addition amount of a waterproofing agent is increased or a hydrophobic resin is used to heighten hydrophobicity for improving the press life, the press life is improved but hydrophilicity is reduced and printing smearing is generated, while when the hydrophilicity is improved, the water-resistanting capability is deteriorated and the press life is lowered.
In particular, there has been a drawback such that in a use atmosphere of high temperature of 30.degree. C. or more, the surface of a printing plate is dissolved in a fountain solution used for offset printing and the press life is lowered and printing smearing is generated. Further, in the case of direct drawing type lithographic printing, since an image area is imaged on an image-receiving layer using oil ink and the like, if adhesive property of the image-receiving layer of the printing plate precursor to the oil ink is not good, even if the hydrophilicity of a non-image area is sufficient and printing smearing as described above is not generated, the oil ink on the image area is dropped out during printing, as a result, press life is deteriorated. This problem has not yet been sufficiently solved up to date.
Moreover, in the recent copied image formation of high degree of resolution using a fine dry toner by an electrophotographic system, for example, in imaging by electrostatic image transfer with a laser printer, etc., to an image-receiving layer, it has been desired that the prevention of stain of the background of a non-image area after transferring should be compatible with the image reproducibility of an image area and printed matters having sharp images and with no stain of a background can be obtained.